금속 산화물 및 이차원 나노 물질 기반의 박막 트랜지스터: 성능 최적화 및 양자점 발광 다이오드에 대한 응용

학위논문(박사) -- 서울대학교대학원 : 공과대학 전기·정보공학부, 2021.8. 곽정훈.박막 트랜지스터를 집적한 전자 디스플레이의 개발은 뛰어난 장점으로 인해 큰 관심을 받아왔다. 지난 수십 년 동안 능동 매트릭스 액정 디스플레이 및 유기 발광 다이오드와 같은 평판 디스플레이에 대한 여러 연구가 보고되었습니다. 이러한 우수한 성과에도 불구하고, p형 산화물/나노 반도체의 개발과 백플레인 박막 트랜지스터로 구동되는 양자점 발광 다이오드의 구동에 대한 연구는 제한적입니다. p형 반도체의 전기적 특성은 이동도가 낮고, 오프 전류가 높으며, 소자의 불안정성이 있기 때문입니다. 이러한 의미에서 우리는 앞서 언급한 응용을 위한 p-형 산화물/나노 물질 기반 박막 트랜지스터와 콜로이드 양자점 발광 다이오드를 연구했습니다. 먼저, 우리는 유연한 전자 장치에 잠재적으로 매력적인 나노 와이어 구조로 형성된 대체 전극으로 전기적 특성을 위해 스프레이 코팅된 단일벽 탄소나노 튜브를 소스 및 드레인 전극으로 사용하는 p 형 주석 산화물 (SnO) 박막 트랜지스터를 구현했습니다. 폴리머 에치 스토퍼 층에 SU-8이 있는 SnO 박막 트랜지스터의 소자 구조는 SnO 채널 층의 열화 없이 원하는 영역에서 단일벽 탄소나노튜브의 선택적 에칭을 가능하게 합니다. 또한 단일벽 탄소나노튜브 전극으로 사용하는 SnO 박막 트랜지스터는 적절한 채널폭과 정규화된 전기적 컨택 특성 (~ 1 kΩ cm), 전계 효과 이동성 (~ 0.69 cm2/Vs), 문턱전압이하 스윙 (~ 0.4 V/dec) 및 전류 온-오프 특성 (Ion/Ioff ~ 3.5×103)을 성공적으로 구현하였습니다. 또한 온도에 따른 전기적 컨택 및 채널 특성은 Ni 전극에 필적하는 적절한 접촉 저항과 함께 무시할 수 있는 수준의 가전자띠 테일 스테이트의 3 x 10-3 eV 활성화 에너지로 SnO 채널 전송을 설명합니다. 둘째, 우리는 먼저 상보형 트랜지스터를 구현하여 p (또는 n 형) MoTe2 박막 트랜지스터에 의해 제어되는 양자점 발광 다이오드 구동을 시연합니다. 이 연구에서는 MoTe2 박막 트랜지스터의 유형 변환을 위해 Poly-L-lysine (PLL)에 의한 분자 도핑을 도입하고, 양자점 발광 다이오드 성능 향상을 위해 표면 리간드 변형을 활용합니다. 이와 관련하여 PLL 처리는 전기적 특성의 저하없이 MoTe2 박막 트랜지스터의 뛰어난 유형 변환을 달성하여, 안정적인 p (또는 n 형) 유형 장치를 확보하여 보완 회로의 가용성을 보장합니다. 또한, 옥틸 아민으로 리간드 치환된 양자점은 양자점 발광 다이오드에서 균형 잡힌 전자/정공 주입을 생성하여, 전류 효율 (ηA = 13.9 cd/A)이 개선되고 수명이 더 길어집니다 (L0 = 3000 cd/m2에서 T50 = 66 h). 결과적으로 MoTe2 박막 트랜지스터는 적절한 스위칭 특성을 가진 디스플레이 백플레인 트랜지스터, 광 전류 생성에 대한 내성 및 작동 안정성을 포함하여 양자점 발광 다이오드를 구동하는 능력을 보여줍니다. 이 논문에서 우리는 유망한 응용을 위한 산화물/나노 물질 기반 박막 트랜지스터와 리간드 치환 기술이 적용된 후면 발광 적색 양자점 발광 다이오드에 대해 논의합니다. 백플레인 박막 트랜지스로 p형 SnO와 MoTe2를 사용하고, 새로운 디스플레이 장치로 CdSe 양자점 발광 다이오드를 사용한 우리의 연구 성과는 융합 연구를 위한 구상 분야에서 잠재적으로 사용될 수 있습니다.The development of electronic displays integrated with Thin Film Transistors (TFTs) has been great interests due to their superb merits. For the past decades, several studies have been reported for the flat-panel displays (FPDs) such as active-matrix liquid crystal display (LCD) and organic light-emitting diode (OLED). Despite of these excellent achievements, progress of p-type oxide/nano semiconductors and operation of quantum dot light-emitting diode (QLED) driven by backplane TFTs are limited. This is because the electrical characteristics of p-type semiconductor have low mobility, high off current, and device instability. In this sense, we investigated p-type oxide/nano material-based TFTs and colloidal quantum dot light-emitting diodes (QLEDs) for the afore-mentioned application. First, we implemented p-type tin oxide (SnO) TFTs with spray-coated single-wall carbon nanotube (SWNTs) as source and drain electrodes for their electrical characteristics as alternative electrodes formed of nanowire structures, which are potentially attractive for flexible electronics. The device architecture of SnO TFTs with a polymer etch stop layer (SU-8) enables the selective etching of SWNTs in a desired region without the detrimental effects of SnO channel layers. In addition, SnO TFTs with SWNT electrodes as substitutes successfully demonstrate decent width normalized electrical contact properties (~1 kΩ cm), field effect mobility (~0.69 cm2/Vs), sub-threshold slope (~0.4 V/dec), and current on-off ratio (Ion/Ioff ~ 3.5×103). Furthermore, temperature-dependent electrical contact and channel properties elucidate SnO channel transports with an activation energy of 3×10-3 eV, interpreted as a negligible level of valence-band tail states, together with decent contact resistance comparable to that of Ni electrodes. Second, we firstly demonstrated the QLEDs operation modulated by p (or n-type) MoTe2 TFTs with the realization of complementary type transistor. In this study, molecular doping by Poly-L-lysine (PLL) as an electron dopant is adopted for a type conversion of MoTe2 TFTs, and surface ligand modification is utilized for the improvement of QLED performance. In this regard, the PLL treatment achieves the outstanding type conversion of MoTe2 TFTs without any degradation of electrical properties, leading to securing reliable p (or n-type) devices, thus, availability of complementary circuits. Furthermore, ligand modified QDs capped with octylamine result in balanced electron/hole injection in QLEDs, yielding improved current efficiency (ηA =13.9 cd/A) and longer lifetimes (T50 = 66 h at L0 = 3000 cd/m2). As a result, MoTe2 TFTs demonstrate their capabilities to drive the QLEDs for the envisioned application including display backplane transistor with decent switching properties, immunity for generation of photocurrent, and operation stability. In this thesis, we discuss the oxide/nano material based TFTs and ligand modified bottom emitting red QLEDs for many promising applications. Our research achievements using p-type SnO and MoTe2 as backplane TFTs, and CdSe QLED as novel display device can be used in potentially envision fields for the convergence research.Chapter 1 1 1.1 An Overview of Thin Film Transistors 1 1.2 An Overview of Quantum Dot Light-Emitting Diodes 8 1.3 Outline of Thesis 13 Chapter 2 15 2.1 Materials 15 2.1.1 Synthesis of ZnO Nanoparticles 15 2.1.2 Synthesis of Red Light-Emitting CdSe/Cd1-xZnxS Quantumd Dots 15 2.2 Device Characterization of Thin Film Transistors 17 2.2.1 Characterization for Thin Film Transistor 17 2.2.2 Characterization of Light Response 18 2.3 Device Characterization of Quantum Dot Light-Emitting Diodes 18 2.3.1 Current-voltage-luminance Measurement of QLEDs 18 2.3.2 Efficiency Calculation Methods 21 2.3.3 Other Characterization Methods 22 Chapter 3 24 3.1 Devic Fabrication of SnO TFTs with Spray-Coated Single Walled Carbon Nanotubes as S/D Electrodes 26 3.2 Electrical Performance of SnO TFTs 30 3.3 Contact Resistance of Spray-coated SWNTs as S/D Electrodes 33 3.4 Summary 40 Chapter 4 41 4.1 Description of QLED display driven by MoTe2 TFTs 45 4.2 Ligand Modification of Red CdSe/Cd1-xZnxS Quantum Dots 49 4.3 Type Conversion of MoTe2 TFTs via Electron-Donated Charge Enhancer 54 4.4 Light-Insensitive Behaviors on Photocurrent Generation in MoTe2 TFTs 61 4.5 Operation of QLEDs Driven by Channel-type Controlled MoTe2 TFTs 66 4.6 Summary 70 Chapter 5 71 Bibilography 73 한글 초록 81박

Effective contracting of uncertain performance outcomes : Allocating responsibility for performance outcomes to align goals across supply chain actors

This dissertation contributes to practice and literature by studying how organizations can effectively contract and sell uncertain performance outcomes. In Chapter 2, I study whether supplier shirking in response to outcome uncertainty can be mitigated by combining performance and behavior specification and evaluation. Based on the findings of this study, I advise purchasing managers to invest in the evaluation of perform

Ubiquitous Integration and Temporal Synchronisation (UbilTS) framework : a solution for building complex multimodal data capture and interactive systems

Contemporary Data Capture and Interactive Systems (DCIS) systems are tied in with various technical complexities such as multimodal data types, diverse hardware and software components, time synchronisation issues and distributed deployment configurations. Building these systems is inherently difficult and requires addressing of these complexities before the intended and purposeful functionalities can be attained. The technical issues are often common and similar among diverse applications. This thesis presents the Ubiquitous Integration and Temporal Synchronisation (UbiITS) framework, a generic solution to address the technical complexities in building DCISs. The proposed solution is an abstract software framework that can be extended and customised to any application requirements. UbiITS includes all fundamental software components, techniques, system level layer abstractions and reference architecture as a collection to enable the systematic construction of complex DCISs. This work details four case studies to showcase the versatility and extensibility of UbiITS framework’s functionalities and demonstrate how it was employed to successfully solve a range of technical requirements. In each case UbiITS operated as the core element of each application. Additionally, these case studies are novel systems by themselves in each of their domains. Longstanding technical issues such as flexibly integrating and interoperating multimodal tools, precise time synchronisation, etc., were resolved in each application by employing UbiITS. The framework enabled establishing a functional system infrastructure in these cases, essentially opening up new lines of research in each discipline where these research approaches would not have been possible without the infrastructure provided by the framework. The thesis further presents a sample implementation of the framework on a device firmware exhibiting its capability to be directly implemented on a hardware platform. Summary metrics are also produced to establish the complexity, reusability, extendibility, implementation and maintainability characteristics of the framework.Engineering and Physical Sciences Research Council (EPSRC) grants - EP/F02553X/1, 114433 and 11394

Management Of Plug-In Electric Vehicles And Renewable Energy Sources In Active Distribution Networks

Near 160 million customers in the U.S.A. are served via distribution networks (DNs). The increasing penetration level of renewable energy sources (RES) and plug-in electric vehicles (PEVs), the implementation of smart distribution technologies such as advanced metering/monitoring infrastructure, and the adoption of smart appliances, have changed distribution networks from passive to active. The next-generation of DNs should be efficient and optimized system-wide, highly reliable and robust, and capable of effectively managing highly-penetrated PEVs, RES and other controllable loads. To meet new challenges, the next-generation DNs need active distribution management (ADM). In this thesis, we study the management of PEVs and RES in active DNs. First, we propose a novel discrete-event modeling method to model PEVs and other loads in distribution networks. In addition, a new optimization algorithm to integrate as many PEVs as possible in DNs without causing voltage issues, including the violation of voltage security ranges and voltage stability, is studied. To further explore the active management of PEVs in the DNs, we develop a universal demonstration platform, consisting of software packages and hardware remote terminal units. The demonstration platform is designed with the capabilities of measurement, monitoring, control, automation, and communications. Furthermore, we have studied the reactive power management in microgrids, a special platform to integrate distributed generations and energy storage in DNs. To solve possible voltage security issues in a microgrid with high penetration of single-phase induction machines under the condition of fault-induced islanding, a voltage-sensitivity-based reactive power management algorithm is proposed

Performance benefits of telerobotics and teleoperation - enhancements for an arm-based tank waste retrieval system

This report evaluates telerobotic and teleoperational arm-based retrieval systems that require advanced robotic controls. These systems will be deployed in waste retrieval activities in Hanford`s Single Shell Tanks (SSTs). The report assumes that arm-based, retrieval systems will combine a teleoperational arm and control system enhanced by a number of advanced and telerobotic controls. The report describes many possible enhancements, spanning the full range of the control spectrum with the potential for technical maturation. The enhancements considered present a variety of choices and factors including: the enhancements to be included in the actual control system, safety, detailed task analyses, human factors, cost-benefit ratios, and availability and maturity of technology. Because the actual system will be designed by an offsite vendor, the procurement specifications must have the flexibility to allow bidders to propose a broad range of ideas, yet build in enough restrictions to filter out infeasible and undesirable approaches. At the same time they must allow selection of a technically promising proposal. Based on a preliminary analysis of the waste retrieval task, and considering factors such as operator limitations and the current state of robotics technology, the authors recommend a set of enhancements that will (1) allow the system to complete its waste retrieval mission, and (2) enable future upgrades in response to changing mission needs and technological advances

The Influence of Employee-Based Brand Equity on the Health Supportive Environment and Culture – Organizational Citizenship Behavior Relation.

PURPOSE: The purpose of this study were (a) to test the validity and reliability of the health-supportive environment and culture scale, (b) to examine the validity and reliability of employee-based brand equity, and (c) to explore relationships among health-supportive environment and culture, employee-based brand equity, job satisfaction, and organizational citizenship behaviors by examining the moderating effect of job level. METHODS: This was a cross-sectional survey of 520 full-time employees (222 men and 298 women) from three places of the largest bookstore in Korea. Exploratory factor analysis and confirmatory factor analysis were performed to obtain factor structure and to evaluate factor validity and reliability in Study 1 (Chapter 2) and 2 (Chapter 3). In Study 3 (Chapter 4), structural equation modeling (SEM) was used to test the proposed model based on Study 1 and 2. RESULTS: Psychometric testing demonstrated satisfactory internal consistency reliability, content and construct validity of the health-supportive environment and culture scale and the employee based brand equity scale. SEM analysis showed that (a) the worksite environment and culture for supporting health had an influence on employee-based brand equity; (b) the health-supportive environment and culture on our findings was not a driving factor of organizational citizenship behaviors; (c) employee-based brand equity affected organizational citizenship behaviors; (d) job satisfaction was influenced by the health-supportive environment and culture, and job satisfaction affected organizational citizenship behaviors; and (e) the moderating effect of job level (i.e., employees vs. managers) was partially supported in the proposed model. CONCLUSIONS: The health-supportive environment and culture scale and employee-based brand equity scale are both reliable and valid measures. Employee-based brand equity in the context of worksite environment and culture for supporting health appears necessary to establish organizational citizenship behaviors. Implications and directions for future research are discussed.PHDKinesiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/99914/1/ybkwon_1.pd

Multi-Agent Systems

A multi-agent system (MAS) is a system composed of multiple interacting intelligent agents. Multi-agent systems can be used to solve problems which are difficult or impossible for an individual agent or monolithic system to solve. Agent systems are open and extensible systems that allow for the deployment of autonomous and proactive software components. Multi-agent systems have been brought up and used in several application domains